The maxtrix proteins of bones and teeth play key roles in the structure and function of these tissues. Our objective in this investigation is to study the biosynthesis of these macromolecules and to understand the regulation of their expression. The expression of bone and enamel matrix proteins have been studied by constructing recombinant cDNA libraries from ameloblast and bone cell mRNA. cDNA clones encoding several bone and tooth matrix proteins were isolated using expressing DNA vectors and polyclonal antisera directed against individual bone matrix and ameloblast proteins. The clones are being used to study the primary structure and regulation of expression of these genes during development and disease.